Kyron Horman The mother of an Oregon boy who vanished nearly two years ago has filed a lawsuit against his stepmother, the last person known to have seen him.The suit filed Friday afternoon in Multnomah County Circuit Court by Desiree Young asks a judge to order Terri Horman to return Kyron Horman or, if he’s dead, to say where his remains are.June 4 “marks two years of this nightmare, two years since my son went missing,” Young said. “I believe that Terri Horman knows where my son is. I believe that Terri Horman is responsible for where my son is.”Attempts by The Associated Press to contact Terri Horman were unsuccessful on Friday afternoon. Stephen Houze, the lawyer representing her in her divorce from Kyron’s father Kaine Horman, did not immediately return a call seeking comment.Investigators have long focused on Terri Horman, although they have not named her as a suspect or filed criminal charges. The suit accuses Terri Horman of kidnapping Kyron, by herself or with help from others.